I've been looking at brownie boxes, aux trannies, to go between the 4L60E and the NVG242 I am planning for the Astrovan. I have 3.73 posi gears, and the mileage is about 14. I got 19 in an astrovan with the same motor, 2wd, same tranny, and 3.08 gears...

I want a .8 o/d, about a 1.25 u/d, and the 1:1 middle gear. Little worried about shifting on the fly with no clutch, but can probably do the bounce the throttle trick to slacken the driveline and quick shift it. Looking at something like a Spicer 4813 (#???), small spicer brownie in any case. There are better crawl type ratios available.

Not responsible for advice not taken...